Neurodegenerative diseases are conditions that affect brain or peripheral nerve function. They result from the deterioration of neurons and they are characterised by progressive central or peripheral nervous dysfunction. They are divided into two groups: conditions causing problems with movement or sensation and conditions affecting memory or related to dementia. Neurodegenerative diseases include: Alexander disease, Alper's disease, Alzheimer's disease, amyotrophic lateral sclerosis, ataxia telangiectasia, Canavan disease, Cockayne syndrome, corticobasal degeneration, Creutzfeldt-Jakob disease, Huntington disease, Kennedy's disease, Krabbe disease, Lewy body dementia, Machado-Joseph disease, multiple sclerosis, Parkinson's disease, Pelizaeus-Merzbacher disease, Pick's disease, primary lateral sclerosis, Refsum's disease, Sandhoff disease, Schilder's disease, Steele-Richardson-Olszewski disease, tabes dorsalis and Guillain-Barre Syndrome. Currently there are no effective cures for these conditions, and very few treatments are available.